Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various layers using lithography to form circuit components and elements thereon.
A transistor is an element that is used frequently in semiconductor devices. There may be millions of transistors on a single integrated circuit (IC), for example. A common type of transistor used in semiconductor device fabrication is a metal oxide semiconductor field effect transistor (MOSFET), as an example. A transistor typically includes a gate dielectric disposed over a channel region in a substrate, and a gate electrode formed over the gate dielectric. A source region and a drain region are formed on either side of the channel region within the substrate.
Source and drain regions in some applications are formed by implanting dopants into the top surface of the substrate at an angle to form implantation regions beneath the gate electrode. However, the doping implantation process requires additional manufacturing steps in the process flow, thus increasing the time required to manufacture the transistors and increasing costs. Furthermore, dopant implantation is difficult to control and may deleteriously affect the stress of the source and drain regions in some applications, decreasing device performance.
Thus, what are needed in the art are improved methods of fabricating transistors and structures thereof.